Field of the Invention
The invention is an apparatus and method for sampling a gas in a container.
Description of Related Art
Fifty-five-gallon steel drums and similar containers are used for the transport and storage of a wide variety of materials, including toxic and non-toxic waste from factories, power plants, laboratories, and environmental cleanup sites. In some cases, the contents of a container or group of containers are completely unknown because information about the contents is lost or was never recorded. In some cases the contents of a container, or one or more of a group of containers, may be suspected of containing a toxic substance or material contaminated with a toxic substance. These situations require a means for sampling the contents of a container in order to establish the identity of its contents and/or to establish whether a particular substance or group of substances are present in the container.
A number of apparatus, methods, and systems have been developed to sample the contents of storage and transport containers. These systems usually involve the collection of a small amount of liquid sample from a container or tank followed by the analysis of the collected sample. Gas chromatography (GC) is one of the most common methods used for the analysis of volatile liquids such as organic solvents, gasoline, and other petroleum-based fuels. GC analysis of a sample usually involves placing a solid or liquid sample containing a volatile substance into a sample vial and obtaining gas from the headspace in the sample vial. Regardless of the analytical method used, obtaining a liquid sample suffers from a number of drawbacks, including the transport of a sample container for analysis of its contents, the eventual disposal of unused liquid, and disposal or cleaning of the sample container.
To overcome at least some of the drawbacks associated with the collection of solid and liquid samples, systems have been developed for obtaining gaseous samples for analysis. For example, U.S. Pat. No. 6,935,199 discloses a headspace gas sampling and venting method in which a first punch having a hollow passage containing a filter and a second punch having a septum are inserted through the lid of a container by a pneumatic gun. A needle is used to obtain a sample the headspace gas in the container through the second punch. The first punch provides an inlet allowing air to enter the container as fluid is removed through the second punch. The sample of headspace gas is placed in a canister and shipped for analysis at a remote site. This system eliminates the collection of non-gaseous samples, but retains the drawback of shipping samples for subsequent analysis and introduces the drawback of requiring a pneumatic gun to insert the first and second punches.
WO 97/47728 discloses monitoring the contents of sealed culture bottles by a sensing unit that is fitted to a sealed container. The sensing unit comprises a housing containing a transducer that is responsive to a sensed property of a liquid in the sealed container and provides electrical outputs proportional to the sensed property to a data processing means. This system provides on-site analysis for bottle-sized containers but requires a sensor for each container being monitored.
Portable electro-chemical sensors may be used to detect and measure volatile substances. For example, a volatile organic compound sensor system disclosed in U.S. Pat. No. 7,487,662, which is incorporated by reference in its entirety, may be used to detect and measure a variety of halogenated volatile organic compounds. The portable sensor is equipped with a probe that can be inserted through a septum into a sealed sampling jar. The probe is connected to a pump that draws gas fluid from the jar and delivers it to a sensor configured to detect one or more chemical species. The probe is designed to allow ambient air to enter the sealed sampling jar as fluid is removed through the probe.
In one aspect, the present invention is an adapter that provides a head space of defined volume outside a storage container inside which volatile substances may be in equilibrium with the contents of the storage container. The headspace inside the adapter may be used to detect and/or measure an amount of a volatile substance using one or more portable sensors without removing a liquid or solid sample from the container.